1. Field of the Invention
The present invention relates to a coating apparatus and an inkjet recording apparatus, and in particular, to a technique for drawing up a coating liquid stored in a coating liquid pan with a roller and roller-coating the drawn coating liquid on a sheet being transported.
2. Description of the Related Art
If printing is performed on a general-use printing sheet (a sheet primarily containing cellulose, such as a coated sheet, for use in offset printing or the like), instead of an inkjet-only sheet, by an inkjet method, feathering, bleeding, or the like may occur, and high-quality printing may not be performed. For this reason, in a system which performs printing on a general-purpose printing sheet by an inkjet method, a processing liquid having a function of aggregating ink is given to the sheet before ink ejection in droplets.
As a system which performs high-speed printing on a sheet by an inkjet method, a system is known, in which a sheet is drum-transported, and printing is performed using a line head. In such system in which a sheet is drum-transported and printing is performed, a method which coats a processing liquid by a roller is suitably used (for example, JP2011-194331A).
In such method according to which a processing liquid is coated by a roller, a coating roller is pressed into contact with a surface of a sheet wound around the circumferential surface of the transport drum and transported, and thereby the processing liquid is coated on the sheet. The supply of the processing liquid to the coating roller is performed by a coating liquid supply roller, and the processing liquid stored in a coating liquid pan is drawn up by the coating liquid supply roller and supplied to the coating roller. That is, a part of the coating liquid supply roller is immersed in the processing liquid stored in the coating liquid pan, and the coating liquid supply roller is brought into contact with the outer circumferential surface of the coating roller, and thereby the processing liquid is given to the outer circumferential surface of the coating roller.
On the other hand, in the coating apparatus configured as above, if the coating apparatus is used for a long period of time, the components of the processing liquid is fixed to the coating liquid pan, and/or foreign substances are mixed with the processing liquid in the coating liquid pan. For this reason, it is necessary to detach and clean the coating liquid pan regularly (so-called maintenance).